Aluminum hydride (AlH3) is one of the most promising hydrogen storage materials that has a high theoretical hydrogen storage capacity (10.08 wt%) and relatively low dehydriding temperature (100–200 ...°C). In this work, we present a cost-effective route to synthesize the α-AlH3 nano-composite by using cheap metal hydrides and aluminum chloride as starting reagents and to achieve liquid state reactive milling. The LiH/AlCl3 and MgH2/AlCl3 reaction systems were systemically explored. The phase identification of the obtained products was carried out by XRD and the morphology observed by TEM characterization. It was found that the α-AlH3 nano-composite can be successfully synthesized by reactive milling of commercial AlCl3 and LiH in a neutral ionic liquid (2-Eim OAc). Based on XRD analysis and TEM observation, an average grain size of 56 nm can be obtained by the proposed mechanochemical process. By setting the isothermal dehydrogenation temperature between 80 and 160 °C, the as-synthesized α-AlH3 nano-composite exhibits an advantage in hydrogen desorption capacity and has fast dehydriding kinetics. The hydrogen desorption content of 9.93 wt% was achieved at 160 °C, which indicates the potential utilization of the prepared nanocomposite in hydrogen storage applications.
In order to improve the particle identification capability, the Beijing Spectrometer (BESIII) collaboration has upgraded the End-cap Time-Of-Flight detector (ETOF) based on Multi-gap Resistive Plate ...Chamber (MRPC) technology. In this paper, the design and engineering development of each part of the project are reported. There are 72 MRPC modules, forming 2 rings. Adjacent modules are staggered placed to avoid dead regions. Each MRPC module contains 12-layer thin gaps to get fast signals with high efficiency and 12 strips to readout the induced signals from two ends, effectively reducing the timing uncertainties from the scattering and positioning. Also, the analog–digital conversion is done near the MRPC and only the digital signals are transferred through thin coax cables, ensuring good signal-to-noise ratio. The complex electromagnetic noises in the BESIII colliding area are well shielded to protect the tiny signals from the MRPC. After careful correction and calibration, the total time resolution of upgraded ETOF system is 65ps.
In the numerical manifold method, there are two kinds of covers, namely mathematical cover and physical cover. Mathematical covers are independent of the physical domain of the problem, over which ...weight functions are defined. Physical covers are the intersection of the mathematical covers and the physical domain, over which cover functions with unknowns to be determined are defined. With these two kinds of covers, the method is quite suitable for modeling discontinuous problems. In this paper, complex crack problems such as multiple branched and intersecting cracks are studied to exhibit the advantageous features of the numerical manifold method. Complex displacement discontinuities across crack surfaces are modeled by different cover functions in a natural and straightforward manner. For the crack tip singularity, the asymptotic near tip field is incorporated to the cover function of the singular physical cover. By virtue of the domain form of the interaction integral, the mixed mode stress intensity factors are evaluated for three typical examples. The excellent results show that the numerical manifold method is prominent in modeling the complex crack problems.
In 1929, H. Weyl proposed that the massless solution of the Dirac equation represents a pair of a new type of particles, the so-called Weyl fermions1. However, their existence in particle physics ...remains elusive after more than eight decades. Recently, significant advances in both topological insulators and topological semimetals have provided an alternative way to realize Weyl fermions in condensed matter, as an emergent phenomenon: when two non-degenerate bands in the three-dimensional momentum space cross in the vicinity of the Fermi energy (called Weyl nodes), the low-energy excitations behave exactly as Weyl fermions. Here we report the direct observation in TaAs of the long-sought-after Weyl nodes by performing bulk-sensitive soft X-ray angle-resolved photoemission spectroscopy measurements. The projected locations at the nodes on the (001) surface match well to the Fermi arcs, providing undisputable experimental evidence for the existence of Weyl fermionic quasiparticles in TaAs.
Using (10 087±44)×10^{6} J/ψ events collected with the BESIII detector, the radiative hyperon decay Σ^{+}→pγ is studied at an electron-positron collider experiment for the first time. The absolute ...branching fraction is measured to be (0.996±0.021_{stat}±0.018_{syst})×10^{-3}, which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be -0.652±0.056_{stat}±0.020_{syst}. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.
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As the staple food of over half the world's population, hot cooked rice high in resistant starch (RS) is of particular interest, which will have greater impact in the dietary prevention of diabetes ...and hyperlipidemia. A mutant rice high in RS in hot cooked rice, described as RS111, was comparatively studied with the wild type and common rice. Despite obviously low RS content in the raw milled rice, the RS content in the hot cooked rice of mutant RS111 was significantly higher than that of the wild type and common rice and, correspondingly, in vitro starch hydrolysis by porcine pancreatic α-amylase tends to be incomplete with low hydrolysis extent for the cooked mutant rice high in RS. Obvious differences in physicochemical properties, starch granule morphology, pasting properties, thermal properties, and X-ray diffraction pattern were observed among the mutant RS111, wild type, and common indica rice. The high-RS mutant was characterized by significantly higher apparent amylose content and crude lipid content, higher percentage of oval-shaped granules and bigger oval size, reduced paste viscosity, and low onset temperature, peak temperature, final temperature, enthalpy of gelatinization, and crystallinity. Keywords: Rice; resistant starch; starch hydrolysis; physicochemical properties; morphology; starch paste properties; thermal properties; X-ray diffraction
In this article, the authors tried to establish a direct correlation between crystallographic variants and impact toughness, and provided some novel insights into the mechanism of cooling rate on the ...impact toughness of coarse grained heat affected zone (CGHAZ) of offshore engineering steel by means of electron back-scattering diffraction (EBSD) analysis. The results showed that variant selection becomes stronger with an decrease in the cooling rate, resulting in the decline of high angle grain boundaries (HAGBs) and thus lower the impact toughness. Moreover, the variation in impact toughness is mainly correlated to the crystallographic block size. The larger the block size, the lower the impact toughness. By visualizing the crystallographic features, it has been clarified that the transition from Bain zone grouping to close-packed plane grouping with the increase of cooling rate, while the corresponding microstructure changes from granular bainite to lath bainite. Furthermore, it has been found that ~ 25% (number fraction) reconstructed prior austenite grains in simulated CGHAZ present a twin-related structure (austenitic twin), which can enhance the variant selection and displays a negative effect on the formation of HAGBs.
Solute atoms segregation to the interfaces, such as grain boundary or twin boundary, often plays a critical role in modulating the properties of a metallic alloy. Deformation induced segregation to ...the interfaces has been a subject of significant research, since this is one of the key issues to fully understand the deformation mechanism and microstructure evolution in service of engineering materials. By means of the high-resolution aberration-corrected scanning transmission electron microscopy (STEM), we report the investigations of segregations to symmetrical boundaries, kink boundary (KB) and twin boundary (TB), in the Mg-Zn-Y alloys containing long period stacking ordered (LPSO) phases subjected to a compression at room temperature. We found that Zn atoms preferentially segregate to the deformation-induced symmetrical KBs in the LPSO structures and sandwiched Mg layers, while only a small amount of Y atoms concentrate at KB in LPSO structure. These enriched atoms may be in a random distribution, form nanoscale clusters or in a periodic pattern. Furthermore, solute atoms would rather decorate the segment of coherent TBs than enrich the overlapped TBs. Based on the direct atomic observations, the segregation mechanisms to the featured microstructures are proposed.
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